Emotion dysregulation has been identified as a critical factor in the development of psychopathology (Cicchetti, Ackerman, &Izard, 1995), and deficits in emotion regulation are a core component of many forms of mental disorders (DelCarmen-Wiggins, 2008). Given its importance, understanding factors that contribute to the development of emotion dysregulation is essential for identifying mechanisms underlying the development of psychopathology. Parents'rearing behaviors have been identified as key predictors of children's emotional reactivity and regulation strategies (Eisenberg, Cumberland, &Spinrad, 1998) and potential targets of intervention. This study aims to examine bidirectional effects between respiratory sinus arrhythmia (RSA), a physiological indicator of emotional reactivity, and parents'rearing behaviors. More specifically, we propose to examine how initial levels and changes in RSA predict anxiety, depression, and disruptive behavior problems in young children, and how parenting shapes children's RSA over time. In addition, children's cognitive self- regulation may interact with emotional reactivity, serving to amplify the effects of emotional dysregulation. Thus, we will consider how these processes may vary across levels of children's self-regulation, identifying how attention and cognitive control may constrain or amplify the relation of emotional reactivity to parenting and psychopathology. In the proposed research, we will assess 174 3-year-old children and their mothers across 3 time points. Two-thirds of families will be from low income or impoverished households, which is associated with higher levels of stress and family disruptions. Therefore, it is expected that children will be at elevated risk for mental health problems. Strengths of the proposed study include the use of physiological and observational measures and longitudinal quantitative methods. PUBLIC HEALTH RELEVANCE: The proposed project aims to meet the strategic planning goals of the National Institute of Mental Health by identifying physiological and environmental mechanisms implicated in the emergence of mental health problems, thereby increasing our ability to predict the development of psychopathology and identify targets for intervention. Importantly, this study proposes to examine these mechanisms during a period of rapid development (physiologically and behaviorally) and heightened neurophysiological plasticity. In addition, consideration of the interplay of individual and environment factors in the development of psychopathology may provide important knowledge that maximizes the effectiveness of interventions.